Thermomagnetic device

ABSTRACT

A thermomagnetic device for generating voltage from heat comprising at least one thin bifurcated ribbon of a thermoelectrically active neutral element or alloy material, the bifurcation therein being positioned substantially centrally on the ribbon, magnet means having a field which is at substantially right angles to the ribbon at the bifurcation, heat and cold source means adapted to form relatively warm and cold portions on the ribbon at the nonbifurcated and bifurcated ends thereof, respectively, and terminal means associated with the bifurcated end of the ribbon.

United States Patent Love [ 51 May 23, 1972 5 4] THERMOMAGNETIC DEVICE Wesley Love, 2472 Observatory Road, Cincinnati, Ohio 45208 [22] Filed: Aug. 26, 1969 [21] Appl.No.: 853,079

[72] Inventor:

[52] US. Cl ..l36/205, 136/200, 62/3, 310/4 [51] Int. Cl. ..H0lv 3/00 [58] Field of Search ..3 10/4; 62/3; 136/200, 205, 136/203, 204, 207

[56] References Cited UNITED STATES PATENTS 3,084,267 4/1963 Newell ..136/207 X 3,343,009 9/1967 Wagini et al. ..136/205 X 3,478,230 11/1969 Otter, Jr. et a1 ..310/4 Primary Examiner-Benjamin R. Padgett Assistant Examiner-Harvey E. Behrend AttorneyMelville, Strasser, Foster & Hoffman ABSIRACT A thermomagnetic device for generating voltage from heat comprising at least one thin bifurcated ribbon of a thermoelectrically active neutral element or alloy material, the bifurcation therein being positioned substantially centrally on the ribbon, magnet means having a field which is at substantially right angles to the ribbon at the bifurcation, heat and cold source means adapted to form relatively warm and cold portions on the ribbon at the nonbifurcated and bifurcated ends thereof, respectively, and terminal means associated with the bifurcated end of the ribbon.

12 Claims, 2 Drawing Figures lNVENTOR/S WESLEY LOVE BY m, Z2;

ATTOR NEYS THERMOMAGNETIC DEVICE I BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to thermoelectric devices and, more particularly to devices utilizing thermomagnetic phenomena.

2. Discussion of the Prior Art The direct conversion of heat to electrical energy, or vice versa, by means of solid-state physical devices, such as, for example, the thermoelectric conversion on the basis of the Seebeck and Peltier effects has long been known.

It is also known to directly convert heat to electrical energy, and vice versa, by utilizing thermomagnetic phenomena known as the Ettingshausen effect (electric production of a temperature gradient; heat pump) and the Ettingshausen- Nernst effect (generating voltage from heat). However, while these thermomagnetic methods have proven to be satisfactory in some respects, they have also proven to be unsatisfactory in other respects, particularly in that they have resulted in low effectivity values and a lower efficiency of performance in com parison with the above mentioned thermoelectric methods on Seebeck and Peltier principals.

SUMMARY OF THE INVENTION The present invention provides an improved thermomagnetic device for generating voltage from heat which gives considerably higher values of thermomagnetic effectivities than heretofore obtainable with similar devices. Additionally, the thermomagnetic device of the present invention also produces a relatively larger current than similar prior art devices and thus eliminates the necessity for use of a delicate readout instrument.

Briefly, in its broadest application, the thermomagnetic device of the present invention includes at least one thin bifurcated ribbon of a thermoelectrically active neutral element or alloy material, the bifurcation therein being positioned substantially centrally on the ribbon. Magnet means having a field is positioned such that the field is at substantially right angles to the ribbon at the bifurcation. Heat source means is adapted to form a relatively warm portion of the ribbon at the nonbifurcated end thereof, and cold source means is adapted to form a relatively cold portion of the ribbon at the bifurcated end thereof. Additionally, terminal means are associated with the legs ofthe bifurcated end of the ribbon.

In operation, pairs of positive and negative charge carriers are generated by the high temperature of the nonbifurcated portion of the ribbon and their flow is induced from the nonbifuracted portion of the ribbon to the bifurcated portion thereof by the thermal gradient in the ribbon caused by the heat and cold source means. Additionally, the positive and negative charge carriers of each of the pairs is separated by the magnetic field such that the positive and negative charge carriers defuse down opposite legs of the bifurcated ribbon. This creates an electromotive force across the bifurcated ends of the ribbon, and thus across the terminal means, providing a steady direct current.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows schematically and in perspective an exemplary embodiment of a thermomagnetic device according to the invention utilizing the Ettinghausen-Nerst effect.

FIG. 2 is an enlarged perspective view of a thin bifurcated ribbon according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, it will be seen that in its broadest application the illustrated thermomagnetic device for generating voltage from heat comprises at least one, and preferably a plurality, of thin bifurcated ribbons 12. The ribbons are made of a thermoelectrically active neutral element or alloy material, such as indium-antimonide, silicon or germanium. However, it will be understood that other materials are known to be satisfactory for this purpose, and the present invention is not limited to those named.

The bifurcation 14 of each ribbon 12, as best seen in F IG. 2, is positioned substantially centrally thereon, and a permanent magnet 18 having a field is associated with each ribbon and positioned such that the field is at substantially right angles to each ribbon 12 at the bifurcation 14. As can be seen, the poles N and S are shown somewhat bent away from each of the ribbons 12 for the purpose of illustration. Actually, the field gap is completely filled by the ribbons 12, or pole shoes of ferrite are inserted between the magnet poles and the adjacent faces of the ribbons 12.

Heat source means 22 and cold source means 24, which are insulated from the magnets 18 to prevent short circuiting, are adapted to form a relatively warm portion and a relatively cold portion on each ribbon 12 at the nonbifurcated end 12a and bifurcated end 12b thereof, respectively. The cold source means 24 may comprise a heat sink which, in the illustrated embodiment, forms a cooling-fin structure for the purpose of cooling the bifurcated end 12b of each ribbon. 12. The cooling-fin structure is, of course, insulated from the ribbons l2.

Terminal means 28, such as the wires 28a, are connected to the legs 16a and 16b, respectively, of the bifurcated portion 12b of each of the ribbons 12.

In operation, the flow of pairs of positive and negative charge carriers (electron-hole pairs) is induced from the nonbifurcated portion 12a of each ribbon 12 to the bifurcated portion 12b thereof by the thermal gradient in each ribbon 12 due to the heat and cold source means 22 and 24, respectively. The positive and negative charge carriers of each of the pairs is separated by the field of the magnets 18 such that the positive and negative charge carriers diffuse down opposite legs 16a and 16b, respectively, of the bifurcated portion 12b of the ribbon 12, causing an electromotive force to be created across the legs 16a and 16b of the bifurcated portion 12b of each ribbon l2, and thus across the terminal means 28 associated with the legs 16a and 16b of the ribbons 12.

In practice, it has been found that best results are obtained when a plurality of ribbons 12 are juxtaposed in the same plane and the magnet 18 includes a plurality of North and South poles around the bifurcated portions 14 of the various ribbons 12, as shown in FIG. 1. Additionally, a first group containing a plurality of ribbons 12 and their magnet 18 may be stacked upon one or more other similar groups.

If a plurality of ribbons 12 are juxtaposed in the same plane to form a group, the terminal means 28, such as the wire 28a, may be connected in series to the legs 16a and 16b of the bifurcated portions 12b of the ribbons 12, the wire 28a joining the leg 16a of each ribbon 12 down which the positive carriers diffuse with the leg 16b of an immediately adjacent ribbon 12 in that group down which the negative carriers diffuse. It should also be noted that the legs 16a and 16b of the juxtaposed ribbons 12 in a group may also be connected in paral lel, in which case, if one or more groups of juxtaposed ribbons 12 are stacked, the nonbifurcated portions 12a of the ribbons 12 may all be formed in one piece. Accordingly, it will be easier to heat the nonbifurcated ends 12a of the ribbons 12.

The efficiency of the thermomagnetic device 10 may be enhanced by doping each of the legs 16a and 16b of each of the ribbons 12 with impurities such that the leg 16a down which the positive charge carriers diffuse has an excess of positive charge carriers and the leg 16b down which the negative charge carriers diffues has an excess of negative charge carriers. For example, if the leg 16a is made of germanium or silicon, the doping impurities therefor could be arsenic or aluminum, respectively. Likewise, if the leg 16b is made of germanium or silicon, the doping impurity therefor could be gallium or phosphorus, respectively.

It should be emphasized that the thermomagnetic device 10 of the present invention supplies a steady direct current and may be used for any number of purposes, such as, for example, to replace thermocouples, etc. However, irrespective of the use to which the device 10 is put, it has been found that the output voltage for each ribbon 12 therein may be calculated according to the following formula, the elements thereof being shown in FIG. 2.

AV= Q H AT,

where Q is the N ernst coefficient of the material;

H is the magnetic field in the z direction; and

AT is the temperature difference between the ends of the ribbon.

I claim:

1. A thermomagnetic device for generating voltage from heat, which comprises:

a. at least one thin bifurcated ribbon of a thermoelectrically active neutral element or alloy material, the bifurcation therein being positioned substantially centrally on said ribbon;

b. magnet means having a field, said magnet means being positioned such that said field is at substantially right angles to said ribbon at said bifurcation;

0. heat source means adapted to form a relatively warm portion of said ribbon at the nonbifurcated end thereof;

d. cold source means adaPted to form a relatively cold portion of said ribbon at the bifurcated end thereof; and

e. terminal means associated with the legs of said bifurcated end ofsaid ribbon,

whereby the flow of pairs of positive and negative charge carriers are induced from the nonbifurcated portion of said ribbon to the bifurcated portion thereof by the thermal gradient in said ribbon due to said heat and cold source means, and said positive and negative charge carriers of each of said pairs is separated by said field such that the positive and negative charge carriers diffuse down opposite legs of said bifurcated ribbon and an electromotive force is created across said bifurcated ends, and thus across said terminal means.

2. The thermomagnetic device according to claim 1, wherein a plurality of said ribbons are juxtaposed in the same plane to form a first group of ribbons, and wherein said magnet means comprises a magnet having a plurality of North and South poles, a North and a South pole being adjacent the bifurcation of each of said ribbons in said group.

3. The thermomagnetic device according to claim 2, wherein said first group of ribbons and magnet are stacked upon at least one substantially identical second group of ribbons and magnet.

4. The therrnomagnetic device according to claim 3, wherein said thermal means associated with the legs of said bifurcated end of said ribbons connect said ribbons in each said group in series by joining the legs of each ribbon down which the positive carriers diffuse with the leg of an immediately adjacent ribbon in that group down which the negative carriers diffuse.

5. The thermomagnetic device according to claim 3, wherein said thermal means associated with the legs of said bifurcated end of said ribbons connect said ribbons in each said group in parallel.

6. The thermomagnetic device according to claim 1, wherein each of said legs is doped with alloy impurities such that the leg down which the positive charge carriers diffuse has an excess of positive charge carriers and the leg down which the negative charge carriers diffuse has an excess of negative charge carriers.

7. The thermomagnetic device according to claim 1, wherein said neutral material is indium-antimonide.

8. The thermomagnetic device according to claim 1, wherein said neutral material is silicon.

9. The thermomagnetic device according to claim 8, wherein said leg down which the positive charge carriers diffuse is doped with aluminum and said leg down which the negative charge carriers diffuse is doped with phosphorus.

10. The thermomagnetic device according to claim I, wherein said neutral material is germanium.

11. The thermomagnetic device according to claim 10,

wherein said leg downwhich the positive char e carriers diffuse is doped with arsenic and said leg down w ich the negative charge carriers diffuse is doped with gallium.

12. The thermomagnetic device according to claim 1, wherein said cold source means comprises a heat sink which forms a cooling-fin. 

2. The thermomagnetic device according to claim 1, wherein a plurality of said ribbons are juxtaposed in the same plane to form a first group of ribbons, and wherein said magnet means comprises a magnet having a plurality of North and South poles, a North and a South pole being adjacent the bifurcation of each of said ribbons in said group.
 3. The thermomagnetic device according to claim 2, wherein said first group of ribbons and magnet are stacked upon at least one substantially identical second group of ribbons and magnet.
 4. The thermomagnetic device according to claim 3, wherein said thermal means associated with the legs of said bifurcated end of said ribbons connect said ribbons in each said group in series by joining the legs of each ribbon down which the positive carriers diffuse with the leg of an immediately adjacent ribbon iN that group down which the negative carriers diffuse.
 5. The thermomagnetic device according to claim 3, wherein said thermal means associated with the legs of said bifurcated end of said ribbons connect said ribbons in each said group in parallel.
 6. The thermomagnetic device according to claim 1, wherein each of said legs is doped with alloy impurities such that the leg down which the positive charge carriers diffuse has an excess of positive charge carriers and the leg down which the negative charge carriers diffuse has an excess of negative charge carriers.
 7. The thermomagnetic device according to claim 1, wherein said neutral material is indium-antimonide.
 8. The thermomagnetic device according to claim 1, wherein said neutral material is silicon.
 9. The thermomagnetic device according to claim 8, wherein said leg down which the positive charge carriers diffuse is doped with aluminum and said leg down which the negative charge carriers diffuse is doped with phosphorus.
 10. The thermomagnetic device according to claim 1, wherein said neutral material is germanium.
 11. The thermomagnetic device according to claim 10, wherein said leg downwhich the positive charge carriers diffuse is doped with arsenic and said leg down which the negative charge carriers diffuse is doped with gallium.
 12. The thermomagnetic device according to claim 1, wherein said cold source means comprises a heat sink which forms a cooling-fin. 